path: root/drivers/xen/grant-table.c

/******************************************************************************
 * grant_table.c
 *
 * Granting foreign access to our memory reservation.
 *
 * Copyright (c) 2005-2006, Christopher Clark
 * Copyright (c) 2004-2005, K A Fraser
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
#include <linux/workqueue.h>
#include <linux/ratelimit.h>

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
#include <xen/interface/memory.h>
#include <xen/hvc-console.h>
#include <xen/swiotlb-xen.h>
#include <xen/balloon.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/interface.h>

#include <asm/pgtable.h>
#include <asm/sync_bitops.h>

/* External tools reserve first few grant table entries. */
#define NR_RESERVED_ENTRIES 8
#define GNTTAB_LIST_END 0xffffffff

static grant_ref_t **gnttab_list;
static unsigned int nr_grant_frames;
static int gnttab_free_count;
static grant_ref_t gnttab_free_head;
static DEFINE_SPINLOCK(gnttab_list_lock);
struct grant_frames xen_auto_xlat_grant_frames;

static union {
	struct grant_entry_v1 *v1;
	void *addr;
} gnttab_shared;

/*This is a structure of function pointers for grant table*/
struct gnttab_ops {
	/*
	 * Mapping a list of frames for storing grant entries. Frames parameter
	 * is used to store grant table address when grant table being setup,
	 * nr_gframes is the number of frames to map grant table. Returning
	 * GNTST_okay means success and negative value means failure.
	 */
	int (*map_frames)(xen_pfn_t *frames, unsigned int nr_gframes);
	/*
	 * Release a list of frames which are mapped in map_frames for grant
	 * entry status.
	 */
	void (*unmap_frames)(void);
	/*
	 * Introducing a valid entry into the grant table, granting the frame of
	 * this grant entry to domain for accessing or transfering. Ref
	 * parameter is reference of this introduced grant entry, domid is id of
	 * granted domain, frame is the page frame to be granted, and flags is
	 * status of the grant entry to be updated.
	 */
	void (*update_entry)(grant_ref_t ref, domid_t domid,
			     unsigned long frame, unsigned flags);
	/*
	 * Stop granting a grant entry to domain for accessing. Ref parameter is
	 * reference of a grant entry whose grant access will be stopped,
	 * readonly is not in use in this function. If the grant entry is
	 * currently mapped for reading or writing, just return failure(==0)
	 * directly and don't tear down the grant access. Otherwise, stop grant
	 * access for this entry and return success(==1).
	 */
	int (*end_foreign_access_ref)(grant_ref_t ref, int readonly);
	/*
	 * Stop granting a grant entry to domain for transfer. Ref parameter is
	 * reference of a grant entry whose grant transfer will be stopped. If
	 * tranfer has not started, just reclaim the grant entry and return
	 * failure(==0). Otherwise, wait for the transfer to complete and then
	 * return the frame.
	 */
	unsigned long (*end_foreign_transfer_ref)(grant_ref_t ref);
	/*
	 * Query the status of a grant entry. Ref parameter is reference of
	 * queried grant entry, return value is the status of queried entry.
	 * Detailed status(writing/reading) can be gotten from the return value
	 * by bit operations.
	 */
	int (*query_foreign_access)(grant_ref_t ref);
};

struct unmap_refs_callback_data {
	struct completion completion;
	int result;
};

static const struct gnttab_ops *gnttab_interface;

static int grant_table_version;
static int grefs_per_grant_frame;

static struct gnttab_free_callback *gnttab_free_callback_list;

static int gnttab_expand(unsigned int req_entries);

#define RPP (PAGE_SIZE / sizeof(grant_ref_t))

static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
{
	return &gnttab_list[(entry) / RPP][(entry) % RPP];
}
/* This can be used as an l-value */
#define gnttab_entry(entry) (*__gnttab_entry(entry))

static int get_free_entries(unsigned count)
{
	unsigned long flags;
	int ref, rc = 0;
	grant_ref_t head;

	spin_lock_irqsave(&gnttab_list_lock, flags);

	if ((gnttab_free_count < count) &&
	    ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
		spin_unlock_irqrestore(&gnttab_list_lock, flags);
		return rc;
	}

	ref = head = gnttab_free_head;
	gnttab_free_count -= count;
	while (count-- > 1)
		head = gnttab_entry(head);
	gnttab_free_head = gnttab_entry(head);
	gnttab_entry(head) = GNTTAB_LIST_END;

	spin_unlock_irqrestore(&gnttab_list_lock, flags);

	return ref;
}

static void do_free_callbacks(void)